The ultimate goal of designers and manufacturers of loudspeaker systems has long been to reproduce sound that qualitatively approaches the actual sound produced during an original event. Early efforts toward improving sound reproduction included the development of stereo loudspeakers. More recent efforts along these lines have included various improvements to stereo speakers and their use.
One such development in the quest for high-fidelity sound reproduction included loudspeaker systems using various forms of reflective surfaces. U.S. Pat. No. 4,256,922 issued to Gorike discloses one such system that employs the walls of a room as passive reflective surfaces. U.S. Pat. No. 4,230,905 issued to Crum et al also discloses a system that utilizes the walls and ceiling of a room as reflective surfaces. Similarly, U.S. Pat. No. 4,805,731 issued to Staley disclose specially designed acoustical reflectors. Such reflective surfaces serve to redirect sound from essentially point source speakers toward a general listening area while simultaneously creating interference patterns that act to enhance the quality of sound reproduction.
Reflective surfaces, however, suffer from the problem of distortion associated with the reflection of low-frequency sound waves. Such distortion results from the fact that, in ordinary speakers, low-frequency sound waves are more widely dispersed than high-frequency sound waves. Various efforts have been undertaken by designers and manufacturers of loudspeaker systems to minimize such distortion. One such approach is disclosed in U.S. Pat. No. 4,227,050 issued to Wilson wherein separate reflective surfaces are dedicated to low and high-frequency sound waves respectively. These reflective surfaces are also designed into the speaker housing itself. Used in conjunction with other reflective surfaces such as the walls, ceiling and floor of a room, the quality of sound reproduction is again enhanced.
Another approach to the problem of distortion associated with the reflection of low-frequency sound waves has been to project low-frequency sound waves directly into the general listening area while simultaneously reflecting high-frequency sound waves. U.S Pat. No. 4,266,092 issued to Barker discloses such a system that utilizes the walls of a room to reflect high-frequency sound waves only in an effort to enhance the quality of sound reproduction.
Reflective surfaces of various shapes and textures have also been used to better control the reflection of sound waves as well as reduce the distortion associated with the reflection of low-frequency sound waves. U.S. Pat. No. 4,190,739 issued to Torffield discloses such a system wherein curved reflectors not only reflect sound waves but concentrate them in an optimal listening area. The use of a roughened surface on such a reflector reduces distortion of reflected low-frequency sound by reducing the angle of dispersion.
Each of the above described efforts toward high fidelity sound reproduction, however, continue to suffer from various problems including continued distortion of reflected low-frequency sound waves and/or a lack of uniform disbursement of the reflected sound waves. Reflected sound waves are often directed toward and lost in non-listening areas or concentrated in a small listening area.
As a result, the ideal method and apparatus for sound reproduction and projection would prevent distortion associated with the reflection of low-frequency sound waves by reflecting high-frequency sound waves only. The ideal method and apparatus for sound reproduction and projection would also reflect high-frequency sound waves through the use of a concave reflective surface that would maximize the uniform disbursement of sound waves into a listening area.